The drive limit of LTO2, I have benchmarked at speeds of 90-94MB/s, 
sustained.  Around 137-138MB/s for LTO3.

Justin.

On Fri, 22 Sep 2006, Weber, Philip wrote:

> I've done lots of dd tests to/from the disk outside of NetBackup, using
> individual LUNs and various filesystems configured in various RAID
> configurations.  Also going by the manufacturer's spec sheets sa to what
> I can expect max (150 Mb/s).  Performance issues manifest themselves as
> soon as I try to write multiple streams to a disk staging filesystem
> whilst also reading off it, though the attempted speed of the writes is
> probably greater (from /dev/random) than I would expect from my
> NetBackup clients.  But it's only got ATA drives.  Because the
> performance is bad before I bring NetBackup into the mix, I haven't
> looked much at tuning NetBackup yet.
>
> My fastest backups are across the SAN fabric using Advanced Client & 4
> streams will run to 1 tape driving it at about 50 Mb/s which may be the
> drive limit (LTO2).
>
> -----Original Message-----
> From: Ed Wilts [mailto:ewilts at ewilts.org]
> Sent: 22 September 2006 12:37
> To: Weber, Philip
> Cc: veritas-bu at mailman.eng.auburn.edu
> Subject: Re: [Veritas-bu] LTO3 and Disk Staging
>
>
> On 9/22/2006 4:19 AM, Weber, Philip wrote:
>> What sorts of disk systems are people using as disk staging to keep
>> LTO3s happy?
>
> We're using HP EVA with FATA (Fibre ATA) drives.  We don't drive the
> LTO3s at full speed, but I do not believe it's an EVA issue.
>
>> Our current EMC Clariion Cx300 struggles to supply data fast enough
>> to 3 LTO2 drives (even outside of NetBackup) and performance goes
>> through the floor if (as is often the case) it is still trying to
>> write backups to disk while streaming data off to tape.
>
> What sorts of benchmarks have you done to prove that it's a disk issue?
>  Have you done something like a dd to see how fast you can read data
> from the disk?  Have you monitored your switch ports?  I've witnessed
> our NetBackup environment hit 150MB/sec on our master server's 2Gbps
> switch port doing a dd from the DSSU to /dev/null.  My destaging
> performance to LTO-3 is normally quite poor so I know I've got a
> NetBackup issue somewhere.
>
>> We have pretty much a 24*7 backup window with lots of slow & small,
>> slow & big, and some fast, clients.
>
> I think that describes most of us...  Do your fast clients drive the LTO
>
> directly at a good speed?
>
>       .../Ed
>
> -- 
> Ed Wilts, Mounds View, MN, USA
> mailto:ewilts at ewilts.org
>
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